The present invention relates to a method and a control system for applying defined clamping forces in a brake that is electrically operable by means of an actuator and includes a first friction surface (friction lining) and a second friction surface (brake disc), wherein a correlation exists between the actuator position and the clamping force, and wherein values of the clamping force as well as of the actuator position are determined, the values being measured by means of a clamping force sensor and a position sensor.
International patent application WO 01/68428 discloses a method and a control system for applying defined clamping forces in a disc brake that is operable by means of an electric motor using a reduction gear. The special features of the prior art method involve that the above-mentioned correlation between the actuator position and the clamping force is illustrated by a mathematical model, preferably by a polynomial of second order. When realizing the prior art method, especially in the lower range of the clamping force, a sensitively adjusted controller is used because the boosting factor of the actuator diminishes gradually in this range. However, a sensitively adjusted controller will augment possibly occurring interferences from outside in the force sensor signal so that driving comfort becomes unsatisfactory in the most unfavorable case. External interferences of this type become conspicuous especially in the lower range of the clamping force because the force sensor operates at its bottom limit of detection. Low-pass filtering of the clamping force signal can eliminate the interferences. However, the result will be an impaired dynamics of control because the filtered signal is available only with a phase shift relative to the original signal.
In view of the above, an object of the invention is to disclose a method and a control system permitting improvement of the control quality of the control system referred to hereinabove.